PATCH: Remove old "copyfile" method from copyfile minion code

It appears that once upon a time the act of copying a file involved reading a file into memory and passing all of that data to a single method on the minion side. That method was called "copyfile". For some reason this method still exists even though it is unused. This patch removes that method. Note that there are several other bits of code in copyfile which are currently unused including the "checksum", "_checksum_blob" and "_backuplocal" methods on the minion side and code supporting the "--force" option in the cmd_module. I think that all of these could be useful in the future which is why I decided not to remove them. -- Marcus